This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Projection systems employed in video display units typically utilize lenses adapted to disperse light in a wide cone. The wide cone of light is usually projected on a screen disposed relatively far away form the projection system. As one of ordinary skill in the art would appreciate, such lenses typically have a structure by which chief light rays are made roughly parallel towards the front of the lens of the projection system. This is usually achieved by embedding an exit pupil deep within the lens, adapting the light rays to be parallel and attain a “wide waist.” In order to further widen the light beam, negative lens elements are disposed subsequent to the parallel rays, thus increasing their divergence.
Although wide-angle projection is common, there are video systems for which the use of wide-angle projection system may not be an optimal choice. In systems such as wedge displays comprising a screen in the form of a wedge, light exiting the projection lens system may be inserted into a small entrance aperture of the wedge display. The light entering the wedge display may be projected at an angle relative to the wedge display, such that the light undergoes multiple total internal reflections as it propagates through the wedge to form an image. In this manner an image can be formed on a screen having a relatively small width. Consequently, due to the small entrance pupil and the manner in which the image is projected thereon, the use of a wide-angle projection system may be incompatible with a use of display device, such as a wedge display. Such incompatibility stems from the large beam size produced by a wide-angle projection system and the small entrance pupil of the display device. This mismatch can cause a general loss of light-coupling efficiency between the display device and the projection system. Ultimately this may degrade the quality of the image displayed on a display device. A system and method that allows the use of wide-angle projection in such circumstances is desirable.